1. Field of the Invention
The present invention relates to adhesive-wrapped elongated elements, such as threadlike or ribbonlike strands of elastic. Specifically, the present invention relates to adhesive-wrapped elongated elements wherein the adhesive forms a substantially continuous helical pattern.
2. Background of the Related Art
The use of elongated elements, such as threadlike or ribbonlike strands of elastic in the manufacture of disposable absorbent products, such as diapers, adult incontinence products, feminine care products, training pants, and the like, is known. In the case of diapers and adult incontinence products, the elastic strands generally are located around the waist of the garment and/or at the leg openings.
Disposable absorbent products, such as diapers, adult incontinence products, and the like, generally comprise an outer cover, a water-pervious inner liner, and an absorbent structure located between the outer cover and inner liner. When elastic strands are employed in the manufacture of such disposable garments, the elastic strands are generally adhered to either the outer cover, the inner liner, or both the outer cover and inner liner. A variety of methods have been proposed for adhering the elastic strands to a substrate, such as the outer cover or inner liner.
For example, U.S. Pat. No. 4,666,542 issued May 19, 1987, to De Jonckheere is directed to a process for the production of disposable diaper panties. The disclosed process starts with a multistrand elastic tape which is separated into two arrays of four individual elastic strands. Each individual strand is passed through a longitudinal groove of an adhesive application unit. The strands are said to be completely coated with a hot-melt liquid adhesive. The strands are then brought into contact with, and adhesively bonded to, a flexible sheet.
Coating the entire surface of the elastic strand employs a relatively large amount of the hot-melt adhesive. For economic reasons, this is often undesirable.
U.S. Pat. No. 4,842,666 issued Jun. 27, 1989, to Werenicz is directed to a process for the permanent joining of stretchable threadlike or small ribbonlike elastic elements to a flat substrate, as well as use thereof for producing frilled sections of film or foil strip. Disclosed is a process for joining elastic elements to a flat substrate by means of an adhesive. The process is characterized in that one disposes; or fixes, in the desired position, one or several elastic elements on a flat substrate, or guides them in the desired position at a distance of from about 0.1 to about 3 centimeters from the flat substrate. The elastic elements and some portion of the adjacent region of the substrate are then covered with a sprayed-on melt adhesive. In the case of guiding at a distance, the elastic elements are then brought into contact with the substrate.
Again, spraying an adhesive on the elastic elements, as well as on adjacent areas of the substrate, employs a relatively large amount of adhesive. Due to the cost of such adhesive, this is not always desirable. Additionally, the elastic strands are often applied to the substrate in a stretched condition so that, when relaxed, the elastic strands contract and form rugosities in the substrate. Application of adhesive to the substrate in an area adjacent the elastic strands may interfere with the formation of the rugosities. Specifically, since the adhesive may be less flexible than the substrate, the presence of the adhesive may reduce the flexibility of the substrate, thereby reducing the ability of the elastic elements to contract the substrate.
U.S. Pat. No. 4,880,420 issued Nov. 14, 1989, to Pomparelli is directed to multiple strand elastic means. Disclosed are elastic means comprising substantially parallel multiple strands of stretched elastic adhered between two layers of a fabric by at least one sinusoidal adhesive line. The use of the sinusoidal adhesive line is said to hold the elastic strand sufficiently in place while using a minimum amount of adhesive. The sinusoidal line of adhesive is described as being applied to the substrate to which the elastic material is to be adhered.
When the adhesive is applied to the substrate, the adhesive almost always covers a portion of the substrate adjacent to the elastic strands. As discussed above, this can interfere with the ability of the elastic strands to gather the substrate. Accordingly, in some instances, it is more desirable to apply the adhesive to the elastic strand rather than to the substrate to which the elastic strand is to be applied. For economic reasons, it is almost always desirable to use the minimum amount of adhesive necessary to achieve the desired results.
It is desirable to provide a method for adhering elongated elements such as elastic strands to a substrate, which method involves the use of the minimum amount of adhesive necessary to obtain the desired degree of adhesion, and which method involves adhesive contacting the substrate where necessary to adhere the elongated element to the substrate. It is this and to related goals to which the present invention is directed.
The present invention provides an elongated element having a substantially continuous filament of adhesive helically wrapped thereon. The helically wrapped adhesive has been found to provide sufficient adhesive to adhere the elongated element to a substrate and yet has been found to require a relatively small amount of adhesive compared to other methods known in the art. Additionally, the helically wrapped adhesive has been found capable of adhering the elongated element to a substrate without coating adjacent areas of the substrate with large amounts of the adhesive. Also disclosed is a process and apparatus for forming the adhesive-wrapped elongated element.